P04C3

What it means

P04C3 is the generic code for a fault in the fuel fill door lock position sensor or switch circuit. The control unit monitors the signal that reports whether the fuel filler door lock is locked or unlocked. It set the code because that signal was missing, out of range, or did not match the commanded lock state. Where this feature is fitted and how it is wired depends on the vehicle, so check the manufacturer data for the model.

Symptoms

• Warning light on, either the engine management light or a related warning
• Fuel filler door will not open, or will not lock
• Fuel filler door lock sounds as if it is working but the door status is wrong
• Difficulty refuelling, or a message about the fuel door on the dash (model dependent)
• Possible evaporative system or related fault codes stored alongside it

Possible causes

• Faulty fuel fill door lock actuator with an integrated position sensor or switchlikely
• Damaged wiring, chafed or broken near the fuel filler flap or rear body flex pointslikely
• Corroded, loose or water-damaged connector at the lock assembly or in the rear body harnesslikely
• Mechanical binding of the fuel door or lock mechanism, from dirt, ice, corrosion or damage after a bump, so the position signal is wrongpossible
• Fault in the control unit that handles the lock, or a blown fuse or poor supply or ground to the circuitpossible
• Outdated or faulty control unit software, where the manufacturer lists it as a known cause for the modelrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, and note any other lock, body control or evaporative codes
2. Check the fuel filler door by hand and by lock and unlock commands, and watch and listen for the actuator moving
3. Visually inspect the fuel filler area for damage, dirt, corrosion, ice or a misaligned door or lock pin
4. Check the relevant fuse and inspect the wiring and connector at the lock assembly for damage, water ingress and corrosion
5. Using the manufacturer wiring diagram, test the supply, ground and signal wires at the lock connector for continuity, shorts and correct voltage
6. Use a scan tool that supports live data to watch the lock position signal change as the lock is operated
7. Test the actuator or sensor against the manufacturer's specification, and check the controlling unit only after the wiring and actuator have been ruled out
8. Check for manufacturer service bulletins or software updates for the model

How to fix

• Repair or replace damaged wiring and clean or renew corroded connectors
• Replace the fuel fill door lock actuator or position switch assembly if it fails testing
• Free, clean and lubricate a binding door or lock mechanism with a suitable product, or repair any damage to it
• Restore the correct supply and ground, and replace a blown fuse once the cause of the failure is found
• Replace or reprogram the controlling unit only when testing confirms a fault, or when the manufacturer lists a calibration update as the cure
• Clear the code after repair and confirm it does not return on a road test and a lock and unlock cycle

Can I keep driving?

Nearby codes

• P04C2GenericFuel Fill Door Unlock Control Circuit High
• P04C4GenericFuel Fill Door Lock Position Sensor/Switch Circuit Range/Performance